What is myelofibrosis (MF)?

Myelofibrosis (MF) is a type of blood cancer that affects the bone marrow. In people with MF, scar tissue builds up inside the bone marrow and blood cells are not made properly. MF can happen at any age, but it is most common in people over the age of 50.

If you have MF, you may have low levels of one type, or more than one type, of blood cell. Some people have low levels of some types of blood cells and high levels of another type.

To make up for the lack of blood cells being made in the bone marrow, other organs in the body start to make blood cells. This is usually the spleen and liver. These organs get bigger as they make blood cells.

Having an enlarged spleen can cause problems. It may:

  • keep blood cells in the spleen instead of releasing them into the blood
  • destroy blood cells.

Both these changes can reduce the number of blood cells in the blood.

To understand myelofibrosis and its treatment, it can help to know more about your blood and bone marrow.

Types of myelofibrosis

  • Primary myelofibrosis (pMF)

    MF can happen in people who have never had problems with their bone marrow before. This is called primary myelofibrosis (pMF).

  • Post-ET myelofibrosis 

    MF can develop in people who have essential thrombocythaemia (ET). This is called post-ET myelofibrosis.

  • Post-PV myelofibrosis 

    MF can also develop in people who have polycythaemia vera (PV). This is called post-PV myelofibrosis.

Symptoms of myelofibrosis (MF)

Some people are diagnosed with MF when they have a blood test for another reason. But most people are diagnosed after going to see their GP with one or more symptoms. These may include:

  • tiredness
  • feeling breathless
  • fevers and night sweats
  • losing weight
  • itchy skin (often after a warm bath or shower)
  • achy or tender bones and joints
  • discomfort in the tummy area (abdomen)
  • feeling full soon after beginning to eat
  • bleeding or bruising more easily
  • having infections one after another.

Possible complications of myelofibrosis

  • Gout

    People with MF can develop red, painful and, swollen joints. This is caused by a condition called gout. Gout can happen when the body breaks down more blood cells than normal.

    When the body breaks down cells it makes uric acid. Normally the kidneys remove this acid from the blood and pass it out of the body in urine (pee). If the body breaks down more cells than the kidneys can get rid of, uric acid builds up in the blood. Crystals that form from the uric acid get into joints and cause the symptoms of gout.

    Gout most commonly affects the big toe, but other joints can be affected. Your doctor will check the level of uric acid in your blood. If it is higher than normal they may give you tablets called allopurinol. Allopurinol prevents gout by helping your kidneys get rid of uric acid.

  • Blood clots

    Some people with MF have a higher risk of developing blood clots. Symptoms can happen because a blood clot (thrombosis) forms.

    If you have any symptoms you think may be caused by a blood clot, contact a doctor urgently. If you cannot speak to a doctor, call 999 for an ambulance or go to A&E.

  • Bleeding or bruising

    Sometimes MF can cause abnormal bruising or bleeding. Bleeding may be heavier than normal and take longer to stop. This can cause symptoms such as:

    • nosebleeds
    • bruising easily
    • abnormal vaginal bleeding
    • bleeding gums very dark stools (poo) or dark vomit, (caused by bleeding in the stomach or bowel).

    Tell your doctor if you notice signs of abnormal bleeding. 

    If you think you are bleeding from the stomach or bowel, or if bleeding is heavy or will not stop, contact a doctor urgently. If you cannot speak to a doctor call 999 for an ambulance or go to A&E.

  • Acute leukaemia

    Some people with MF develop acute myeloid leukaemia (AML). AML is a blood cancer, which can get worse quickly if it is not treated. It can cause similar symptoms to MF. But the symptoms of acute leukaemia develop more quickly and can be more severe. Not everyone with MF has the same risk of developing AML. Your doctor can tell you more about this.


Diagnosis of myelofibrosis (MF)

Your GP may have suspected MF based on the results of a blood test (full blood count). You are usually diagnosed with MF after seeing a doctor who specialises in treating blood disorders (haematologist).

Your haematologist will usually arrange some tests for you before they diagnose MF. These help to rule out other conditions that can also affect your blood counts.

  • Blood tests to check for gene changes

    Genes carry the instructions a cell needs to work properly. Certain genes control how many blood cells the bone marrow makes. Changes (mutations) in some of these genes can cause primary myelofibrosis.

    You usually have blood tests to check if you have any of these gene changes. These changes happen in the cells during your life. It is not a gene change you were born with and cannot be passed on in your family.

    Changes in the following genes can cause MF: 

    • JAK2 – over 58 in a 100 people (58%) with primary myelofibrosis have a change in the JAK2 gene.
    • CALR – about 25 in a 100 people (25%) with primary myelofibrosis have a change in the CALR gene
    • MPL – about 8 in a 100 people (8%) with primary myelofibrosis have a change in the MPL gene.

    About 10 in a 100 people (10%) with primary myelofibrosis do not have a change in any of these genes. This is called triple negative MF.

  • Bone marrow test

    Your doctor may want to take a sample of bone marrow (biopsy) to look at under a microscope. They usually remove it from the back of your hip bone (pelvis).

  • Scans

    You may have a scan to show if your spleen or liver is enlarged or if blood is being made anywhere outside your bone marrow. You may have one or more of the following scans:

    • CT scan, which takes a series of x-rays that build up a 3D picture of the inside of the body
    • MRI (magnetic resonance imaging) scan, which uses magnetism to build up a detailed picture of areas of your body
    • Ultrasound scan, which uses sound waves to build up a picture of the organs inside your tummy (abdomen) and pelvis.

Your doctor or nurse will tell you more about these tests.

Waiting for test results can be a difficult time. It may help to talk to your family, friends or specialist nurse.

Treatment of myelofibrosis (MF)

MF cannot usually be cured. In some people it can remain stay the same for many years without causing problems. In others it can become more serious, or even life-threatening.

Your doctor will assess the MF and grade it as low, medium (intermediate) or high risk. This can help you and your doctor to choose the best treatment options for you.

The risk of MF is based on several things, including:

  • your age
  • your symptoms
  • if you have anaemia (low levels of red blood cells)
  • the number of white blood cells in your blood
  • the number of immature (blast) cells in your blood.

If you do not have symptoms, you may not need treatment for a while. But your haematologist will monitor your condition regularly. If you develop any symptoms between appointments let your haematologist or specialist nurse know.

You may be invited to join a clinical trial looking at new ways of treating MF.

Targeted therapy and immunotherapy drugs

Targeted therapies are drugs that block the growth of cancer cells. They do this by interfering with specific molecules that affect how cancers grow and divide. Immunotherapy drugs use the immune system to find and attack cancer cells. These include:

  • Ruxolitinib (Jakavi®)

    Ruxolitinib is a targeted therapy drug. It targets the genes that help the abnormal blood cells in MF to grow. You take it daily as a tablet.

    You may have ruxolitinib to help with symptoms. If you have higher risk MF, it can also reduce an enlarged spleen. The most common side effects are anaemia and reduced numbers of platelets in the blood.

    If you have ever had HIV, hepatitis B or C or tuberculosis (TB), ruxolitinib may make it active again. Your doctor will give you treatment to reduce the risk of this happening.

    It is important to check with your doctor before having any vaccinations. This is because live vaccines may cause an infection in people taking ruxolitinib.

  • Thalidomide

    Thalidomide is also a targeted therapy drug. You may have it on its own, or with steroid tablets. Thalidomide can cause birth defects, so your doctor will talk to you about pregnancy prevention.

  • Interferon alpha

    This is a type of immunotherapy drug. Interferon is a protein produced by the body, but it can also be made as a drug.


Chemotherapy uses anti-cancer (cytotoxic) drugs to destroy cancer cells. It can help reduce the size of the spleen and the liver. It also helps control other symptoms and may increase the number of blood cells.

Hydroxycarbamide (HC) is a chemotherapy drug that is often used to treat MF.

Taking HC for a long time can increase your risk of getting skin cancer. It is important that you protect your skin from the sun. You should also check for any changes in your skin during and after treatment with HC. Your haematologist or specialist nurse can tell you more about this.

Chemotherapy is not suitable for everyone with MF. It temporarily affects the way the bone marrow works and may reduce the level of blood cells. If you have chemotherapy, your doctor will monitor you closely. They will explain the possible side effects of any chemotherapy drug they recommend for you.

Treating anemia

If you have symptoms caused by a low red blood cell count (anaemia), you may have treatment to help.

  • Blood transfusion

    You may have blood transfusions. You can usually have a blood transfusion as a day patient. Most people can have blood transfusions as often as needed.

  • Danazol

    You may be given danazol to help improve anaemia.

  • Steroids

    Steroids are drugs that are sometimes used to treat low levels of red blood cells.

  • Erythropoietin

    Erythropoietin is a drug that may help to increase the levels of red blood cells in some people. You have it as an injection under the skin.

Removing the spleen (splenectomy)

If your spleen is enlarged and causing symptoms, your specialist may talk to you about having surgery to remove it.

There can be advantages and disadvantages to having this operation. Your specialist will talk to you about this before you decide.



If you cannot have surgery to remove the spleen, it may be possible to shrink it with radiotherapy. Radiotherapy uses high-energy rays to destroy cancer cells. It can help to improve symptoms, such as pain and a high platelet count. But the effects may only last for a few months.

Radiotherapy can cause temporary side effects, but they are usually mild. They include tiredness and skin irritation.

Donor stem cell transplant (allogeneic transplant)

If you have higher risk MF and your general health is good, your haematologist may talk to you about having a donor stem cell transplant. This treatment can sometimes cure MF. But it can also cause severe side effects, so it is not suitable for everyone. You and your doctor will need to consider the possible advantages against the risks of having this treatment.

Living with myelofibrosis (MF)


You will need to have regular check-ups and blood tests. If you have any problems or notice new symptoms between appointments, tell your nurse or doctor as soon as possible.

Your feelings

Everyone has their own way of dealing with the different feelings they experience. You may find it helpful to talk things over with family and friends, or your specialist doctor or nurse.

Macmillan is also here to support you. If you would like to talk, you can:

The organisations below also offer information and support: 

  • MPN Voice

    MPN Voice is a support network for people with MPNs (myeloproliferative neoplasms) providing information and support.

  • Leukaemia Care

    Leukaemia Care is a national blood cancer support charity for people with leukaemia and other blood disorders. It has regional support groups.

  • Blood Cancer UK 

    Blood Cancer UK is a blood cancer research charity that provides information and support on any type of blood cancer.

Reviewed: 08 November 2019
Reviewed: 08/11/2019
Next review: 08 May 2022
Next review: 08/05/2022

This content is currently being reviewed. New information will be coming soon.